1. Field of the Invention
The present invention relates to a decontamination method for decontaminating a hermetically sealed decontamination chamber and a decontamination subject placed inside the hermetically sealed decontamination chamber, and a decontamination apparatus.
2. Background of the Invention
There are several conventional methods for decontaminating hermetically sealed decontamination chambers and decontamination subjects (empty syringe outer tubes used for producing pre-filled syringes, and the like) placed in the hermetically sealed decontamination chambers. For example, using a gas generating apparatus, hydrogen peroxide gas is generated; this hydrogen peroxide gas is charged in the hermetically sealed decontamination chamber; the room temperature of the hermetically sealed decontamination chamber is lowered to saturate the hermetically sealed decontamination chamber; and a thin film of a condensed liquid layer of hydrogen peroxide is formed on the inner wall of the hermetically sealed decontamination chamber and the outer surface of the decontamination subject (e.g., see in general Japanese Laid Open Patent Application No. S61-4543). Furthermore, the higher the hydrogen peroxide concentration for this condensed liquid layer, the higher the decontamination effect. The decontamination described above includes chemical decontamination, sterilization, disinfection, and the like.
However, according to the conventional method described above, the concentration of hydrogen peroxide in the condensed liquid layer, once it has been formed, decreases as time passes, and the decontamination effect is lowered. This is for the following reason. Because the hydrogen peroxide contained in aqueous hydrogen peroxide has a higher boiling point than water, when the room temperature of the hermetically sealed decontamination chamber is lowered and the condensed liquid layer is formed, the hydrogen peroxide begins to condense first to form the liquid layer, and then afterwards water vapor begins to condense. In other words, in the initial stage of the process of condensation, a condensed liquid layer with a high hydrogen peroxide concentration is formed, but after a certain amount of time, the water vapor begins to condense, and the overall hydrogen peroxide concentration is lowered. For example, by evaporating 35% aqueous hydrogen peroxide to generate hydrogen peroxide gas, in the initial period of the condensation process, a condensed liquid layer with a concentration of 58% is formed. However, after a certain amount of time, the concentration is reduced to near 35%.